The present invention relates to an improved suspension for vehicles particularly for vehicles such as trucks which are designed to carry heavy loads. It is known that leaf spring suspensions are well suited to support heavy loads and give the driver a good perception of the vehicles's behavior through the steering column. However, trucks with leaf spring suspensions are relatively hard riding, and further when a truck is under a heavy load, steering of the truck is unstable.
Previous attempts to provide a smooth ride with stable steering included the systems disclosed in U.S. Pat. Nos. 4,998,749 and 4,397,478. These patents are intended to improve the ride and handling of heavy load vehicles; however, the prior art still lacks the responsive steering and handling that is desired by a truck driver.
Accordingly it is an object of this invention to provide a suspension system for combining the advantageous feature of leaf spring suspension and a rubber or air suspension to provide comfortable driving and riding conditions and excellent responsive steering for a heavy duty vehicle. The inventive suspension has flexibility to provide improved ride, better control of steering, and improved overload capabilities.